Brush fibres and brush construction employing same



June 21, 1966 J. c. LEWIS, JR., ETAL 3,256,545

BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME Filed Dec. 16, 1963 7 Sheets-Sheet 1 INVENTORS JOHN C LEWIS Jr GILBERT SHAW BY MORGAN,FINNEGAN, DURHAM 8u PINE ATTORNEYS June 21, 1966 J. c. LEWIS, JR.. ETAL 3,

BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME Filed Dec. 16, 1963 v Sheets-Sheet 2 Fig-8 Fig-l0 Figl3 INVENTO S JOHN C. LEWIS,Jr. GILBERT SHAW BY MORGAN, FINNEGAN, DURHAM 8x PINE ATTORNEYS June 21, 1966 J. c. LEWIS, JR., ETAL 3,256,545

BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME Filed Dec. 16, 1963 7 Sheets-Sheet 3 INVENTORS JOHN C. LEWIS, Jr GILBERT SHAW BY MORGAN,FINNEGAN, DURHAM 8 PINE ATTORNEYS J1me 1965 J. c. LEWIS, JR. ETAL 3,256,545

ATTORNEYS June 21, 1966 J. c. LEWIS, JR. ETAL 3,256,545

BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME Filed Dec. 16, 1963 7 Sheets-Sheet 6 INVENTORS JOHN C. LEWlS,Jr. GILBERT SHAW NN E BY MORGAN,FINNEGAN, DURHAM 8 PINE ATTORNEYS June 1966 J. c. LEWIS, JR., ETAL 3,

BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME Filed Dec. 16, 1963 7 Sheets-Sheet 7 INVENTORS JOHN C LEWIS Jr GILBERT SHAW BY MORGAN, FINNEGAN, DURHAM 8 PINE ATTORNEYS United States Patent 3,256,545 BRUSH FIBRES AND BRUSH CONSTRUCTION EMPLOYING SAME John C. Lewis, Jr., and Gilbert Shaw, both care of Polymers, Inc., Middlebury, Vt. Filed Dec. 16, 1963, Ser. No. 331,004 13 Claims. (Cl. -159) This relates to thermoplastic brush fibres having improved characteristics, particularly improved wear resistance. The invention also includes novel brush constructions employing the fibres of this invention.

The improved charactertistics of the brush fibres of the invention are attained by locating the greatest possible percentage of the brush fibres mass at or near their working ends and utilizing unique cross-sectional area and cross-sectional shape changes along the brush fibre lengths to make the resultant unconventional working tips operate as effective brush working ends.

Prior to this invention, thermoplastic brush fibres have made limited use of change in cross-sectional area of material or shape along their length to improve their utility.

Thermoplastic brush fibres have, on occasion, had a uniform taper imparted to them to give fibres of changing cross-sectional area with reduced diameter working tips and coarse butts thereby simulating the general longitudinal shape of hog bristles and other brush fibres occurring in nature. Compressible thermoplastic brush fibres have been spatulated as in co-pending application Serial No. 217,000, now Patent No. 3,184,822, filed August 15, 1962 by Gilbert Shaw to produce brush fibres with changing cross-sectional shape but constant cross-sectional area of material. Extruded and cut brush fibres have had their tips sanded, rounded and flagged or split for specific uses. Thermoplastic brushes have been molded containing integral tapered brush fibres but these brush fibres have necessarily tapered towards their working ends otherwsie it would not have been possible to remove the molded brushes from their molds.

It will be apparent in the discussion which follows wherein the novel brush fibres of the invention differ from prior brush fibres and it should also be apparent why the improved brush fibres offer superior wear resistance among other advantages.

Objects and advantages of this invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the steps, methods, combinations and improvementspointed out in the appended claims.

An object of this invention is to provide novel brush fibres having improved wear-resistance.

Another object of this invention is to provide novel brush fibres which will give longer service than other brush fibres of similar materialwhich do not have their maximum percentage of material mass arranged at or near their working tips.

It is yet a further object of this invention to reduce the percentage of original brush fibre weight that is discarded in worn-out brushes.

A still further object of this invention is to provide novel brush construction employing brush fibres having the qualities set forth in the foregoing objects.

Another object of this invention is to provide novel segments comprising brush fibres secured together in molding which may be further assembled into a wide variety of brushes.

It has been found that the objects of this invention may be realized by forming a molded fibre having different cross-sectional areas of material along its length, said fibre having an abrasion-resistant zone and a stem zone.

ice

In order to provide high Wear-resistance, it is desired that the average weight per'unit length of the abrasion resistant zone be at least 10% greater than the average weight per unit length'in the stem zone. Fibres of good abrasion resistance and suitable fluxural characteristics with accompanying economic advantages are obtained when the minimum cross-sectional area of the stem zone is less than the average cross-sectional area of the abrasion resistant zone. invention are those having different cross-sectional shapes along their length. By such construction, it is possible to obtain fibres having a good overall balance of abrasionresistance, flexural characteristics and recovery characteristics.

In the drawings:

FIGURE 1 is a front view of a brush fibre of this invention having a bulbous working end providing an abrasion resistant zone attached to a stem providing a stemzone having less cross-sectional area of material than the working end.

FIGURE 2 is a front view of the brush fibre of FIG- URE 1 connected to another bulbous Working end by a common stem whose cross-sectional area of material is less than that of the connected bulbous working ends.

FIGURE 3 is a side view of the double fibre of FIG- URE 2 doubled through a bend of degrees at about its mid-point.

FIGURE 4 shows a front view of a further embodiment of brush fibre having different cross-sectional areas of material wherein the fibre incorporates a tapered section as its working end, the stem being uniform in cross section and having less cross-sectional area of material than the tapered working end.

FIGURE 5 shows a front view of yet another embodiment of a brush fibre illustrating the invention in which the cross-sectional area of material diminishes constantly from the working tip to the non-working end, the crosssection shape being of circular cross-section'al shape at the working end (see FIGURE 6) and Y cross-sectional shape at its non-working end (see FIGURE 7).

FIGURE 6 is a cross-sectional view taken along the line VI-VI of FIGURE 5.

FIGURE 7 is a cross sectional view taken along the lines VII-VII of FIGURE 5.

FIGURE 8 shows a double brush fibre consisting of the fibre of FIGURE I joined to the fibre of FIGURE 5.

FIGURE 9 shows the composite double fibre of FIG- URE 8 doubled through a bend of 180 degrees at about its mid point.

FIGURE 10 is a front view of .an embodiment similar to that of FIGURE 1 but of Y-shaped cross-section instead of circular.

FIGURE 11 is a cross-sectional view taken along the lines XI-XI of FIGURE 10.

FIGURE 12 is a cross-sectional view taken along the lines XIIXII of FIGURE 10.

FIGURE 13 is a front view of a different embodiment of fibre illustrating a multiple tip fibre.

FIGURE 14 is a front view of a different embodiment of multiple tip fibre.

:FIGURE 15 is a front view of a multiple fibre arrangement showing double fibres interconnected through the stem portions.

FIGURE 16 is a side view of the embodiment of FIG- URE 15 showing how the connecting means may be made thin enough to give a hinge efiect.

FIGURE 17 is an isometric view illustrating how the interconnected fibres of FIGURE 15 may be retained by a wire in normal strip brush construction.

FIGURE 18 is a front view showing a multiplicity of the fibres similar to those in FIGURE 1 but having a longer stem portion joined at one common end by means Molded fibres included within thisof a connecting segment to give a section having a multiplicity of protruding brush fibres.

FIGURE 19 is a side view of the arrangement of FIG- URE 18.

FIGURE 20 is a front view showing how the protruding fibres of FIGURE 18 may have waves or crimps aolded into them to simulate the irregularities of natural res.

FIGURE 21 is a side view of FIGURE 20 showing how the wave or crimp may be imparted to the fibres in a second plane.

FIGURES 22-26 illustrate a method of assembling a brush using the sections of FIGURE 18. FIGURE 22 is a front view of a section comprising a multiplicity of fibres joined by a common segment. FIGURE 23 is a side view of FIGURE 22. FIGURE 24 is a side view of three sections aligned side by side. FIGURE 25 is an end view of a cap adapted to be placed over the aligned segments of FIGURE 24 in the manner shown in end view 26 which shows a finished brush construction with the sections riveted together and a handle screwed into the cap.

FIGURE 27 is a front view showing how the segment for joining the fibres may be of a circular type.

FIGURE 28 is an isometric view showing how a multiplicity of sections of FIGURE 27 may he slipped over a central shaft and keyed thereto to give a rotary brush.

In order to describe the invention more fully, reference is now madeto the specific embodiments illustrated in the drawings.

The brush fibre shown in FIGURE 1 is of generally circular cross-section and comprises a bulbous working end 1 attached to a stem 2 having a smaller cross-sectional area of material than the bulbous working end. The bulbous working end or abrasion resistant zone provides more than normal material to resist abrasion whereas the slimmer stem or stem zone may be designed to impart desired flexural characteristics into the fibre. The point of attachment of the fibre to a brush body is at 3. It is apparent that if the cross-sectional area of the stem material was increased along with the cross-sectional area of the material in the working end to give more mate-rial at the working ends to resist abrasion, a construction would soon be arrived at in which the increased stiffness of the fibres would render the finished brush too stiff for its intended purpose.

FIGURE 2 shows the brush fibre of FIGURE 1 connected at 3' to a similar fibre with bulbous circular working end -1 attached to stem 2' of smaller cross-sectional area of material than bulbous end 1. As shown in FIG- URE 3, when the double fibre is .bent 180 degrees around 3' and fastened in the direction C thru 3 as in standard brush manufacturing practice, two brush fibres wit-h bulbous ends and slimmer stems emerge which are similar to the brush fibre of FIGURE 1.

FIGURE 4 shows a front view of a brush fibre having its maximum cross-sectional area of material at its working tip 4, a decreasing cross-sectional area in the tapered zone between tip 4 and an intermediate point 5, and a zone of uniform cross-section from 5 to 6, the point of attachment. The cross-sectional shape may vary along the length of the fibre in addition to the cross-sectional area differences noted.

The brush fibre 7 in FIGURE 5 has constantly decreasing cross-sectional area from its working tip 8 to point of attachment 9. In addition it has differing crosssectional shape along its length, said fibre being of circular sectional shape near its working end as shown in FIG- URE 6 and gradually changing into Y cross-sectional shape near its non-working end as shown in FIGURE 7; the web length to web thickness ratio of the Y-shaped portion of the fibre being at least 4:1 for reasons pointed out hereinafter.

In FIGURE 8, the fibre of-FIGURE 1 is shown connected to the fibre of FIGURE 5 at point 9' to give a double brush fibre of unique form. Of course, where the stems of the fibres of FIGURES 1 and 5 are joined there is a gradual transition from a circular-cross-section to a Y-shaped cross-section. The aforedescribed fibre when bent double upon itself at 9' as shown in FIGURE 9 and retained in the direction of C as in conventional brush construction gives two fibres which are within the scope of the invention.

The fibre 10 of FIGURE 10 has a cross-section of Y shape in the stem zone as described in our co-pending patent application Serial No. 231,779 filed October 19, 1962, now Patent Number 3,121,040 which describes unoriented polyolefin filaments of high recovery nature consisting of connected webs whose web length to web thickness ratios as in RtS in FIGURE 11 is in the order of at least 4: 1. Such shapes would provide optimum high recovery characteristics to the zones of the fibres where specific fiexural characteristics were desired while the attached fibre ends having R25 ratios below a 4:1 ratio as shown in FIGURE 12 or any other selected shape would provide the ultimate in wear.

Referring back to FIGURE 3 it is apparent that if the twin bulbous end zones 1 and 1 were to be worn down in service until the fibre length of bulbous nature was used up between the extremities and point 3 and. the brush with the remaining fibre was discarded, the percentage of unused fibre being discarded would be of a much smaller proportion of the original fibre in the brush than would be the case if the fiber was of uniform cross-section or tapered towards the working ends. It is further apparent that the use of shapes as described in our above-mentioned copending application No. 231,779 would permit material economies in sections 2 and 2 of FIGURE 3 that would make the portion of original filament discarded in a wornout brush still less.

It has been found that a number of small cross-sectional area working tips with the same cross-sectional tip area of a lesser number of larger tips will wear just as long as the aggregate with the larger tips. For more efiicient and effective sweeping action therefore it is desirable to produce filaments with numerous working tips. Such filaments 11 and 12 are shown in FIGURE 13 and in FIG- URE 14, respectively.

The multiple tips shown in FIGURES 13 and 14 may be of different length thereby accomplishing in a new manner the difference in fibre lengths that is a characteristic of natural brush fibres. These multiple tips may have their maximum cross-sectional different distances from the working ends for purposes of most effective brush action.

If so desired as shown in FIGURE 15, pairs of filaments of FIGURE 1 may be interconnected at 13. Such a junction could be yet further slimmed down as shown in FIGURE 16 to give a hinge 14, which would permit ready doubling of the fibre arrangement.

The embodiment of FIGURE 17 comprises the connected and doubled over fibre arrangement of FIGURE 15, retained by a wire 15, in a metal channel 16. This is normal assembly for strip-type brushes except that the fibres have not hitherto been interconnected.

Fibres, similar to those of FIGURE 1 but having longer stems, can have at one common end their stems molded together to give constructions as shown in FIGURES 18 and 19 in which the stern ends are an integral part of the connecting segment 17.

The embodiment of FIGURE 20 is a modification of the interconnected fibres of FIGURE 18 in which a wave or curve 18, is imparted to the fibres simultaneously with their forming. Waving can be effected in a second plane as shown by the wave 19 in FIGURE 21. Such waves are to simulate the wavy nature of natural brush fibres.

FIGURES 22-26 show how segments with protruding filaments illustrated in FIGURE 18 may be assembled. into a finished brush. More particularly, as shown in FIGURES 22 and 23, fibres 21 of this invention protrude from a common segment 22. The common segment 22,

bears holes 23, or other means for attaching it to other similar segments. A side view of this segment is shown in FIGURE 23. In FIGURE 24 three similar segments 22, 22' and 22" are placed so that the holes 23, are aligned with similar holes 23 and 23" in sections 22' and 22". As shown in FIGURE 25, there is provided a molded cap 24, with three sets of holes 25, which are spaced the same as holes 23, 23' and 23" in the corresponding segments 22, 22' and 22". When cap 24 is placed over segments 22, 22' and 22" as shown in FIG- URE 26 and rivet type attachments 26 are driven through the matching holes of the cap and the three segments and a handle 27, is screwed into cap 24, a finished brush emerges as shown in FIGURE 26.

As shown in FIGURE 27, fibres 28 of the invention may be made integrally with a circular central segment 29. By placing a multiplicity of such integral circular shapes as shown in FIGURE 28 with suitable key slot 30, in the direction D on to a shaft 31, with key 32, to be located as at 30, a rotary brush mounted on shaft 31, may be readily fabricated.

In each of the embodiments illustrated in the drawings, and described hereinbefore in order to provide a working zone of high abrasion-resistance, the average weight per unit length of the working zone is at least greater than the average weight per unit length in the stem zone. In all of the illustrated embodiments, the minimum crosssectional area of the stem zone is less than the average cross-sectional area of the abrasion resistant zone. Fibres of the aforedescribed type exhibit a combination of high abrasion resistance and good flexural characteristics with accompanying economic advantages.

Fibres of the type illustrated in FIGURES 5 and 10 having a stem portion of Y cross-section shape, with a web length to web thickness ratio of at least 4:1 in addition to improved wear resistance and satisfactory fiexural characteristics, exhibit high recovery characteristics.

The brush fibres of this invention may be best fabricated by use of molding technique, and preferably by injection molding. The thought of molding such fibre shapes represents a completely new approach to brush 7 fibre manufacture.

It is a well known fact that unoriented products are softer and less stiif than oriented products. The concept of molding unoriented brush fibres is thereby eased as unoriented fibres are larger than oriented fibres for a given stiffness. The magnitude of the fibres described in the invention is such that the maximum cross-sectional area of the fibres is in the range of 0.006 to 0.200 square inch and their minimum cross-sectional area is in the range of 0.003 to 0.150 square inch.

In fabricating the molded fibres of this invention, there is employed a mold having a cavity of such configuration that there may be formed therein a fibre having the desiredconfiguration which in all instances is a fibre having different cross-sectional areas of material along its length including an abrasion resistant zone and a stem zone. A sufiicient amount of melted thermoplastic material to form the desired fibre is passed into said mold cavity, preferably by injection although transfer feeding procedures may also be employed. On cooling of the thermoplastic material the desired fibre is produced and then removed from the mold cavity.

As indicated heretofore, the filaments of this invention are preferably fabricated by injection molding employing the usual injection molding techniques such as those described in the article entitled, Injection Molding Operation appearing in Modern Plastics Encyclopedia, vol. 40, No. 1A, September 1962, pages 722-743. Of course, the temperature and pressures employed vary depending upon the nature of' the thermoplastic material that is employed and the form and weight of the molded filament. For example in producing a filament of poly propylene (the polypropylene raw material being sold under the trade name Moplen), the cylinder temperature, i.e. the temperature to melt the thermoplastic material, should be maintined between 200 C. and 260 C. (392-500" F.) and the nozzle'temperature should be 10-20 C. (50-68 F.) lower than that of the cylinder. The pressure should not be lower than 1200 kg./cm. (about 17,000 p.s.i.). In machines with preplasticizer, however, lower pressures of from 800-1200 kg./cm. (about 1l,000l7,000 p.s.i.) may be used. In producing said polypropylene filaments, the mold temperature can range from 20 to C. (68176 F.).

The following example illustrates the fabrication of a molded filament of the type shown in FIGURE 1, the chemical composition of the thermoplastic material employed being a molding grade polypropylene material (e.g. Moplen, Shell Polypropylene 5620, etc.) containing 1% black composite.

Polypropylene is first melted in the screw-type cylinder of a conventional injection molding machine at 425 F. and is then by an injection stroke forced through a nozzle (at 375 F.) into the mold cavity (at 175 F.) using a pressure of approximately 15,000 psi. The total cycle is 16 seconds. The mold itself consists of a two-section mold having one half of the fibre profile of the type shown in FIGURE 1 on each side of the parting line, and the length of the fibre in the same plane as the parting line. The fibre cavity consists of two zones, one zone being 7 inches in length and having a cavity diameter of 0.050" and the other zone being 5" in length and having a cavity diameter of 0.150". Thus the resulting molded fibre from the aforedescribed molding operation is 12 inches long.

It is apparent that most of the fibre embodiment illusstrated in the drawings, i.e. those of a relatively complicated construction, could not be produced by any technique other than molding. In addition, even with respect to fibres of simple construction such, for example, the fibre of FIGURE 1, molding is preferred since it permits fabrication of the fibres in a precise and uniform manner Included Within the scope of this invention, however, are those fibres of novel construction having incorporated therein the principles of this invention with respect to providing fibres of improved abrasion-resistance, by increasing the cross-sectional area of material at the working end but which are capable of fabrication although not as efficiently, by procedures other than molding, e.g. extrusion. Such novel fibres are exemplified by the embodiment of FIGURE 1 and may be defined as a thermoplastic brush fibre having different cross-sectional areas of material along its length, said fibre comprising an abrasion resistant zone and a stem zone Whose cross-sectional area of material is less than the average cross-sectional area of material of the abrasion-resistant zone, said brush fibre having a portion along its length of uniform cross-sectional area of material The data reported in Tables I and II which follow show clearly the improvement in wear-resistance that can be obtained by increasing the cross-sectional area at the working end. In obtaining the data reported in the tables, apparatus and procedure used were as follows:

The apparatus used was an end-test apparatus whereby an end of a fibre was subjected to reciprocating movement (8" path, 24 cycles per minute) across the surface of emery cloth held under a load of grams throughout. New emery cloth was used for each test. The emery cloth surface was cleaned when wear measurements were taken. Throughout all of the tests, wear measurements were taken every 15 minuttes.

The data reported in Table I which follows brings out two significant points' First, for a fixed load, fibre wear as expressed in percentage of length of fibre lost by abrasion decreases proportionately as the fibre area being abraded increases. Secondly, for each brush fibre material using fixed loading, the product obtained by multiplying the area in square inches exposed to the abrading action, in this instance the number of fibres times the fixed cross-sectional area of each fibre and the distance worn off the aggregate end gives a reasonable constant. It can be shown that the constant varies from material to material.

The invention in its broader aspects is not limited to the compositions, combinations and improvements described but departures may be made therefrom in the scope of the accompanying claims without departing from In Table I, the reference numerals (1) to (7) in the principles of the invention and without sacrificing its the heading of the various columns refer to the following: hief advantages (1) Cross-sectional shape. What claimed (2) Number of Strands tested. 1. A thermoplastic brush fibre of improved abrasion (3) Area in Square inches for Single fibra resistant characteristics, said fibre having different cross- (4) Total time fibre was tsted sectional areas of material along its length comprising an (5) Wear measumd in thousmdths of aninch' elongated abrasion resistant zone and an elongated inte- (6) Percent wear is distance worn/ original length 100. gml Stem Zone of 165561 cross-Sectional area than he (7) Ne constan'gzdisiange wo 'nxnumbgr of fib X abrasion resistant zone, said abrasion resistant zone having cross-sectional area of each fibre. a uniform cross-sectional area of material along its length,

TABLE I Fibre Shape (1) Type Strands (2) Area (3) Time (4) Wear (5) Percent Wear Wear (6) Constant (7) Propylene... 1 0.0 2 hrs 0. 36 57. 5 0.0025 D0 s. 2 0.007 2 hrs 0.14 22.5 0.0020 s 0. 007 2 hrs 0. 11 17. 5 0. 0023 4 0. 007 2 hrs 0. 07s 12. 5 0. 0022 5 0 007 2 hrs 0. 002 10. 0 0. 0022 0 0. 007 2 1ns. 0. 047 7. 5 0. 0020 Table II presents equally signi cant data obtained from the average weight per unit length of the abrasion rethe aforeclescribed test apparatus.

It shows first that unoriented polyallomer has a wear constant that is reasonably consistent but which is in the order of three times that of oriented polypropylene. This would mean generally that three times the area of unoriented polyallomer would be required at the working end of a brush in order to have it wear down at the same rate as oriented polypropylene. In actual practice in rotary street-cleaning brushes the longer performance of oriented polypropylene brushes as compared to unoriented polya lomer brushes with comparable weight of fibre bears this general consideration out.

Secondly, Table II shows that a greater number of fiiament aggregate ends of given end cross-section wears to the same degree as one filament with equivalent crosssection. Samples 1, 2 and 3 illustrate the point. Again, sample 4 shows that its better wear versus sample 3 is due to the larger cross-sectional area of its tips where the number of tips tested is the same. 1

It should be appreciated that while the examples in Tables I and II dealt with polymer compositions of the polyolefin type, other thermoplastics such as polyamides would give excellent brush fibres of the type covered by the invention. Colorants, extenders, plasticizers and sistant zone being at least 10% greater than the average weight per unit length in the stem zone.

2. A thermoplastic brush fibre according to claim 1 wherein at least part of the stem zone has a cross-section consisting of interconnected webs whose length to web thickness is a least about 4: 1.

3. A thermoplastic brush fibre according to claim 1 wherein there is an abrasion resistant zone at each extremity of an integral common stem zone.

4. A brush element comprising a plurality of molded thermoplastic brush fibres of the type set forth in claim 3 wherein the fibres are integrally joined together through their common stems.

5. A brush construction comprising the fibre arrangement of claim 4 doubled through 180 degrees at approximately their mid-points and retained in that position by suitable support means.

6. A brush construction comprising a plurality of fibres of the type set forth in claim 3 doubled 180 degrees at approximately their mid-points and retained in this position by suitable support means.

7. A thermoplastic brush fibre according to claim 1 wherein the thermoplastic material is selected from the group consisting of polyolefins and polyamides.

8. A brush element comprising a plurality of molded modifiers may be added to these materials as practice dicrate thermoplastic brush fibres of the type set forth in claim 1 TABLE 11 Sample No. Fibre Shape (1) Type Strands (2) Area (3) Time (4) Wear (5) Percent Wear Wear (6) Constant (7) 1 Polyallomer Y Uuorientedni 1 0.039 0.15 25.0 0.0059 2 1 d 3 0. 010 0. 22 35. 0 0. 0000 3 0. 013 0. 17 27. 5 0. 0000 a 0. 010 0. 14 22. 5 0. 0007 The foregoing considerations conclusively demonstate wherein the fibres are integrally joined together at their the advantages to be gained by providing fibres with the free stem ends by a common segment. greatest possible percentage of the brush fibres mass at 9. A brush element according to claim 8 wherein the or near their working ends. When such techniques are common segment is a circular central segment. used in conjunction with stems of high recovery described 10. A brush construction comprising a plurality of the hereinbefore in detail, the brush fibres of the invention integrally connected brush fibres of claim 9 wherein the approach their ultimate in utility. circular central segments are keyed together.

11. A brush construction comprising a multiplicity of brush fibres of the type set forth in claim 1 supported at their stem ends by suitable fibre support means.

12. A molded thermoplastic brush fibre of improved abrasion resistant characteristics, said fibre having an abrasion resistant zone and an integral stem zone, said abrasion resistant zone having a plurality of parallel, elongated working ends integrally connected to one end of said stern zone in substantially axial alignment therewith, the average weight per unit length of the composite of the elongated Working ends being at least 10% greater than the average weight per unit length in the stem zone.

13. A brush construction comprising a multiplicity of the fibres of the type set forth in claim 12 supported by suitable support means.

References Cited by the Examiner UNITED STATES PATENTS 944,009 12/1909 Bernis 15-187 X 1,549,857 8/1925 Eckart 15-181 X 1,946,283 2/1944 Hotfman et a1 15-159.1 2,338,735 1/1944 Person 264-328 2,418,344 5/1947 Goldberg 15-187 10 Booth 264-243 X Cloyd 264-328 X Peterson 15-159.1 Sawyer 264-328 X Collins et a1. 15-187 X Kutik 300-21 X Dant 15-202 Solomon 300-21 X Ulrich 15-159.1 X Sidelman 15-159.1 Dutt 15-187 X Charvat 15-179 X Shaw et a1 15-159.1 Lilley 15-159.1 Schad 15-187 Trotin 15-159 FOREIGN PATENTS CHARLES A. WILLMUTH, Primary Examiner. PETER FELDMAN, Assistant Examiner. 

1. A THERMOPLASTIC BRUSH FIBRE OF IMPROVED ABRASION RESISTANT CHARACTERISTICS, SAID FIBRE HAVING DIFFERENT CROSSSECTIONAL AREAS OF MATERIAL ALONG ITS LENGTH COMPRISING AN ELONGATED ABRASION RESISTANT ZONE AN ELONGATED INTEGRAL STEM ZONE OF LESSER CROSS-SECTIONAL AREA THAN THE ABRASION RESISTANT ZONE, SAID ABRASION RESISTANT ZONE HAVING A UNIFORM CROSS-SECTIONAL AREA OF MATERIAL ALONG ITS LENGTH, THE AVERAGE WEIGHT PER UNIT LENGTH OF THE ABRASION RESISTANT ZONE BEING AT LEAST 10% GREATER THAN THE AVERAGE WEIGHT PER UNIT LENGTH IN THE STEM ZONE. 